Electric steam generator having molded plastic lid and base secured together by a snap-fit connection arrangement

ABSTRACT

A portable electric wallpaper steamer has a generator (G) including a base (1) and lid (2), both injection molded of plastic material. An elastomeric sealing ring (29) is seated in a recess in a circumferential interengagement zone between the lid and base and is held compressed by the interengagement of engagement members (24) on the lid with cooperating engagement members (39) on the base. The lid-engagement members (24) and base-engagement members (39) comprise integrally molded parts of the lid and base and one or both are resiliently deformable so that they can be brought into snap-fit engagement with each other by downward movement of the lid relative to the base to form a steam pressure tight seal. An electric heating element (6) is mounted in the base for heating water therein to generate steam. The lid includes a handle (9), filling port (10), safety valve (13) and a steam outlet port (21) connected to a wall paper steaming plate (W) by a pipe.

FIELD OF THE INVENTION

The invention relates to a steam generator particularly, though notexclusively, for use in a wallpaper steamer.

BACKGROUND OF THE INVENTION

Wallpaper steamers are known for moistening old wallpaper so that it canbe readily removed from walls prior to redecorating.

In a steam generator for a prior wallpaper steamer, we attach the lid tothe base of the steamer by means of C-section metal strips slid ontoabutting flanges of the lid and base--which are of moulded plasticsmaterial. This means of attachment of the lid is restrictive on thedesign of the generator--i.e. requiring straight runs of the strip alongthe joints, making the generator rectangular. The strips add expense andassembly cost.

The present steam generator has been developed as a simpler, cheaperproduct.

Plastics material containers are known in which the lid resilientlyengages the base and seals sufficiently tightly for storage of food forinstance at ambient pressure. The lid has a circumferential groove intowhich an upstanding rim of the base extends. This arrangement isinadequately pressure tight for a steam generator. In particular aseparate sealing element appears to be necessary.

THE INVENTION

A steam generator of the invention comprises:

a moulded plastics material base including a sidewall;

a moulded plastics material lid;

the lid and the base defining between them a circumferentialinter-engagement zone;

the lid having at the inter-engagement zone at least one engagementmember with an engagement face directed generally away from the base(when assembled thereto);

the base having at the inter-engagement zone at least one engagementmember with an engagement face directed generally away from the lid(when assembled thereto);

an electrical heating element mounted in the base; and

an elastomeric sealing ring arranged on assembly, around thecircumferential inter-engagement zone, between the base and the lid;

the lid- and base-engagement members engaging via their engagement faceswith resilient deformation of either or both of the lid- andbase-engagement members on assembly of the lid to the base so as tocompress the sealing ring for sealing contact with both the base and thelid.

Preferably, the engagement face(s) of at least one of the lid- andbase-engagement members is a lip adapted and arranged to engage thecorresponding engagement face of the other engagement member(s). In thepreferred embodiment, the engagement faces of both of the lid- andbase-engagement members are respective lips, each adapted and arrangedto engage the corresponding lip on the corresponding other engagementmember. Conveniently, one of the lid- and base-engagement membersextends generally towards the base or lid respectively and the other ofthe engagement members extends adjacent to the one engagement member(when assembled thereto).

Preferably, one or other of the base and lid, conveniently the base,includes a recessed seat for the elastomeric sealing ring and the otherof the base and the lid has a plain sealing surface opposite therecessed seat. The recessed seat and the plain sealing surface arepreferably arranged inwardly of the lid- and base-engagement members.

It is envisaged that the lid- and the base-engagement member(s) may becontinuous circumferentially around the lid and the base. However if theor each lid-engagement member is arranged outwardly of the respectivebase-engagement member, its lip is difficult to remove from the mouldingtool unless an expensive/complex tool is used. If a continuousbase-engagement member engaging outside the lid-engagement member isused, even more severe difficulties are encountered. Accordingly it ispreferred to employ a plurality of separate individual engagementmembers distributed circumferentially around the lid and the base.Moulding difficulties may still be encountered if the lid engagementmembers are outermost; accordingly they are preferably provided inwardlyof the base engagement members and respective apertures are providedbetween the sidewall of the base and the individual base-engagementmembers for receiving the corresponding lid-engagement members. Thisarrangement permits a simple mould to be used.

The radially inner edge of each aperture may be provided with astiffening flange, conveniently connected to the sidewall by one or morestruts, and the corresponding lid-engagement member may be provided withan anti-disengagement surface, conveniently on a rib, abutting thestiffening flange.

The individual base-engagement members are preferably interconnected bycircumferential continuations and connected to the base by radial webs.

Advantageously, location flanges are provided separate from, andradially outward from, but in circumferential continuation of thelid-engagement member for location outside the mentioned circumferentialcontinuations. Conveniently, each of the circumferential continuationsis stepped to provide a lower portion having a radially outer surfaceflush with a radially outer surface of the corresponding said locationflange.

Preferably, a further, continuous inner flange is provided on theunderside of the lid, inwardly of the engagement members to locate thelid on the base by engagement therewith radially inwardly of the seatfor the sealing ring. The lid may also include at least one upstandingflange for reinforcement of the lid to exert compression on the sealingring.

The lid is preferably substantially flat, although slightly upwardlydomed. Conveniently it incorporates a carrying handle, a safety valve, afiller cap inlet and steam outlet.

To help understanding of the invention, a specific embodiment thereofwill now be described with reference to the accompanying drawings, inwhich:

THE DRAWINGS

FIG. 1 shows in a perspective view a wallpaper steamer including a steamgenerator of the invention and a wall plate;

FIG. 2 is an underneath plan view of the steam generator of FIG. 1;

FIG. 3 is a cross-sectional view on the line III--III in FIG. 2;

FIG. 4 is a rear view of the steam generator;

FIG. 5 is a fragmentary cross-sectional view on the line V--V in FIG. 1of an inter-engagement zone of the lid and base of the steam generator;and

FIG. 6 is a fragmentary underneath view in the direction of arrow VI ofthe detail shown in FIG. 5.

Referring to the drawings, the wallpaper steamer shown in FIG. 1comprises a steam generator G and a hollow-underside wall plate Winterconnected by a pipe P. In use, water is boiled in the generator Gto form steam which is led by the pipe P to the wall plate W forapplication to wallpaper to be steamed and stripped.

The steam generator G comprises a base 1 and a lid 2, both beinginjection mouldings of plastics material, preferably heat stabilizedpolypropylene. As shown in FIGS. 3 and 4, the base has a centraldepression 3 in which an electrical heating element 4 is disposed andfrom which radiate a series of fins 5 (FIG. 2) for stability of thesteam generator. The heating element 4 is of the type conventionallyused in kettles. A stainless steel plate 6 is secured by the fitting 7of heating element 4 to extend between the heating element 4 and thebottom wall 8 of the central depression to protect the latter in theevent of the steam generator boiling dry.

The lid 2 is domed slightly upwardly and has an integrally mouldedcentral carrying handle 9, a filling inlet 10 with a pressure tightmoulded plastics cap 11. Upstanding from the bottom of the base 1 is alevel indicating finger 12 which is visible through the inlet 10 withthe cap 11 removed. On the opposite side of the handle 9 from the inlet10 is a safety valve 13 comprised of a moulded plastics plunger 14 witha stem 15 and a head 16. The stem 15 carries a circlip 17 and a spring18 which biases the plunger 14 downwards for captivation of an O-ring 19between the head 16 and the lid 2 around an aperture 20. The spring 18is light, allowing the safety valve 13 to open at 4 psig (approximately0.25 bar). The lid 2 also incorporates a moulded, threaded outlet spout21 to which the pipe P is connected by a union 22.

Referring now to FIG. 5 in particular, the engagement of the lid 2 withthe base 1 will be described. FIG. 5 shows the inter-engagement zone ofthe lid 1 and the base 2. In this zone the lid 2 has an annular region23 outwardly of which it has at an even radius a series of eight equallycircumferentially spaced, downwardly depending individual engagementmembers 24. Discrete and outwardly from these downwardly depend outerlocation flanges 25, circumferentially occupying the spaces between theindividual engagement members 24. Inwardly of the annular region 23 acircumferentially continuous, inner location flange 26 extends. In theinterengagement zone, the base 1 has an outwardly extending rim 27,having an annular recess 28 which provides a seat for a closed cellneoprene foam sealing ring 29, which on assembly, as shown in FIG. 5, iscompressed between the plain undersurface 30 of the lid 2 at its annularregion 23 and the recess 28. Above the surface 30, the lid has a firstupstanding flange 31 for reinforcing it to exert compression on thesealing ring 29. A second reinforcement flange 32 extends around the lid2 radially further out above its engagement members 24.

At the position of each lid-engagement member 24, an aperture 33 isprovided in the rim 27 of the base 1, which rim otherwise extends out toa downwardly depending flange 34. Circumferentially positioned on eachside of each aperture 33 is a radial web 35 extending between thesidewall 36 of the base 1 and the flange 34. The flange 34 has an outerstep 37 for accommodating the outer location flanges 25 and providing asubstantially flush exterior. The inner location flange 26 engageswithin the base sidewalls 36. Thus the lid is both centred on the baseand stiffened in the inter-engagement zone.

The lid-engagement members 24 each have an upwardly turned lip 38 ontheir radially outer surface with an engagement face directed away fromthe base 1. The flange 34 at the apertures 33 is in effect a series ofbase-engagement members 39, each of which has a downwardly turned lip 40with an engagement face directed away from the lid. On assembly of thelid 2 to the base, the lid-engagement members 24 flex inwardly andresiliently snap out when the lips 38,40 have passed and inter-engage attheir engagement faces. This is the position shown in FIG. 5, in whichthe sealing ring 29 is compressed. To resist unintentional disengagementof the lips 38,40 and their engagement members 24,39, the lid-engagementmembers 24 are provided on the inside with ribs 41 which at theirsurface 42 abut the base 1 at the apertures 33. The inner edge of theapertures 33 are stiffened by flanges 43, each of which is supported bytwo integral struts 44 extending back to the sidewall 36.

It will be appreciated, from FIG. 5 that the particular arrangement ofthe lid-engagement members 24 being discrete and with the lips 38 ontheir outer sides, that the moulds for both the base 1 and the lid 2have no overhanging parts necessitating expensive, complex moving partsof the moulds.

I claim:
 1. A steam generator for generating steam at a pressure greaterthan ambient atmospheric pressure, comprising:a moulded plastic base (1)including a sidewall (36); a moulded plastic lid (2); the lid (2) andthe base (1) defining between them a circumferential inter-engagementzone; the lid (2) having at the inter-engagement zone at least oneengagement member (24) with an engagement face (38) directed generallyaway form the base (1), when assembled thereto; the base (1) having atthe inter-engagement zone at least one engagement member (39) with anengagement face (40) directed generally away from the lid (2), whenassembled thereto; an electrical heating element (4) mounted in the base(1); and an elastomeric sealing ring (29) arranged on assembly, aroundthe circumferential inter-engagement zone, between the base (1) and thelid (2); the lid-engagement and base engagement members (24, 39)engaging via their engagement faces (38, 40) with resilient deformationof either or both of the lid-engagement and base-engagement members (24,39) on assembly of the lid (2) to the base (1) so as to compress thesealing ring (29) for sealing contact with both the base (1) and the lid(2), for containing steam in the generator at a pressure greater than anambient atmospheric pressure; and means (P, W) for providing the steamfrom the generator at the pressure greater than the ambient atmosphericpressure.
 2. A steam generator according to claim 1, wherein theengagement face(s) of at least one of the lid- and base-engagementmembers is a lip (38) adapted and arranged to engage the correspondingengagement face (40) of the other engagement member(s).
 3. A steamgenerator according to claim 2, wherein the engagement faces of both ofthe lid- and base-engagement members are respective lips (38,40), eachadapted and arranged to engage the corresponding lip on thecorresponding other engagement member.
 4. A steam generator according toclaim 1, wherein one of the lid- and base-engagement members (24,39)extends generally towards the base or the lid (1,2) respectively and theother of the lid- and base-engagement members extends adjacent to theone of the said engagement members (when assembled thereto).
 5. A steamgenerator according to claim 1, wherein one or other of the base and lidincludes a recessed seat (28) for the elastomeric sealing ring (29) andthe other of the base and the lid has a plain sealing surface (30)opposite the recessed seat.
 6. A steam generator according to claim 5,wherein the recessed seat (28) and the plain sealing surface (30) arearranged inwardly of the lid- and base-engagement members (24,39).
 7. Asteam generator according to claim 5, wherein the recessed seat (28) isprovided on the base.
 8. A steam generator according to claim 1, whereinthe lid- and the base-engagement members are circumferentiallydiscontinuous around the lid and the base and are provided,circumferentially around the lid and the base, as a plurality ofindividual engagement members (24,39).
 9. A steam generator according toclaim 8, wherein the individual lid-engagement members (24) are providedinwardly of the corresponding individual base-engagement members (39).10. A steam generator according to claim 9, wherein respective apertures(33) are provided between the sidewall (36) of the base and theindividual base-engagement members (39) for receiving the correspondinglid-engagement members (24).
 11. A steam generator according to claim 9,wherein radial webs (35) are provided to connect the individualbase-engagement members (39) to the sidewall of the base.
 12. A steamgenerator according to claim 9, wherein circumferential continuations(34) are provided to interconnect the individual base-engagement members(39).
 13. A steam generator according to claim 1, wherein the lidincludes an inner flange (26) for engaging inside the sidewall (36) ofthe base and inwardly of the recessed seat (28)-for the sealing ring(29).
 14. A steam generator according to claim 1, wherein the lidincludes a handle (9), a filling port (10), a steam outlet port (21) anda safety valve (31).
 15. A steam generator comprising:a moulded plasticbase (1) including a sidewall (36); a moulded plastic lid (2); the lidand the base defining between them a circumferential inter-engagementzone; the lid having at the inter-engagement zone at least oneengagement member (24) with an engagement face (38) directed generallyaway from the base (1); the base having at the inter-engagement zone atleast one engagement member (39) with an engagement face (40) directedgenerally away from the lid (2); an electrical heating element (4)mounted in the base (1); and an elastomeric sealing ring (29) arrangedon assembly, around the circumferential inter-engagement zone, betweenthe base (1) and the lid (2); the lid- and base-engagement members (24,39) engaging via their respective engagement faces (38, 40) withresilient deformation of both or either of the lid- and base-engagementmembers (24, 39) on assembly of the lid (2) to the base (1) so as tocompress the sealing ring (29) for sealing contact with both the base(1) and the lid (2); respective engagement faces (38, 40) of at leastone of the lid- and base-engagement members (24, 39) being a lip (38)adapted and arranged to engage a corresponding engagement face (40) ofthe other engagement members; one of the lid- and base-engagementmembers (24,39) extending generally towards the base or the lid (1,2)respectively and the other of the lid- and base-engagement membersextending adjacent to the one of the said engagement members; the lid-and the base-engagement members (24,39) being circumferentiallydiscontinuous around the lid (2) and the base (1) and provided,circumferentially around the lid (2) and the base (1), as a plurality ofindividual engagement members (24,39); and apertures for said one of thelid- and base-engagement members (24,39) being provided at said other ofthe lid- and base-engagement members (24,39).
 16. A steam generatorcomprising:a moulded plastic base (1) including a sidewall (36); amoulded plastic lid (2); the lid (2) and the base (1) defining betweenthem a circumferential inter-engagement zone; the lid (2) having at theinter-engagement zone at least one engagement member (24) with anengagement face (38) directed generally away form the base (1), whereineach engagement member (24) is circumferentially discontinuous; the base(1) having at the inter-engagement zone at least one engagement member(39) with an engagement face (40) directed generally away from the lid(2), wherein each engagement member (39) is circumferentiallydiscontinuous around the base; an electrical heating element (4) mountedin the base (1); and an elastomeric sealing ring (29) arranged onassembly, around the circumferential inter-engagement zone, between thebase (1) and the lid (2); wherein the lid-engagement and base-engagementmembers (24, 39) engage via their engagement faces (38, 40) withresilient deformation of either or both of the lid-engagement andbase-engagement members (24, 39) on assembly of the lid (2) to the base(1) so as to compress the sealing ring (29) for sealing contact withboth the base (1) and the lid (2), wherein each lid engagement member(24) is provided inwardly of the corresponding base-engagement member(39), when assembled thereto; and wherein respective apertures (33) areprovided between the sidewall (36) of the base and the individualbase-engagement members (39) for receiving the correspondinglid-engagement members (24), and wherein the radially inner edge of eachaperture (33) is provided with a stiffening flange (43) and thecorresponding lid-engagement member (24) is provided with ananti-disengagement surface (42) abutting the stiffening flange (43) whenassembled thereto.
 17. A steam generator according to claim 16, whereinone or more support struts (44) is provided to connect each stiffeningflange (43) to the sidewall of the base.
 18. A steam generatorcomprising:a moulded plastic base (1) including a sidewall (36); amoulded plastic lid (2); the lid (2) and the base (1) defining betweenthem a circumferential inter-engagement zone; the lid (2) having at theinter-engagement zone at least one engagement member (24) with anengagement face (38) directed generally away form the base (1), whereineach engagement member (24) is circumferentially discontinuous; the base(1) having at the inter-engagement zone at least one engagement member(39) with an engagement face (40) directed generally away from the lid(2), wherein each engagement member (39) is circumferentiallydiscontinuous around the base; an electrical heating element (4) mountedin the base (1); and an elastomeric sealing ring (29) arranged onassembly, around the circumferential inter-engagement zone, between thebase (1) and the lid (2); wherein the lid-engagement and base-engagementmembers (24, 39) engage via their engagement faces (38, 40) withresilient deformation of either or both of the lid-engagement andbase-engagement members (24, 39) on assembly of the lid (2) to the base(1) so as to compress the sealing ring (29) for sealing contact withboth the base (1) and the lid (2), wherein each lid engagement member(24) is provided inwardly of the corresponding base-engagement member(39), when assembled thereto; wherein circumferential continuations (34)are provided to interconnect the individual base-engagement members(39); and wherein the lid includes location flanges (25), providedseparate from and radially outward from but in substantialcircumferential continuation of the individual lid-engagement members(24), for location outside the circumferential continuations (34) of theindividual base-engagement members.
 19. A steam generator according toclaim 18, wherein each of the said circumferential continuations (34) isstepped (37) to provide a lower portion having a radially outer surfaceflush with a radially outer surface of the corresponding said locationflange (25).
 20. A steam generator comprising:a moulded plastic base (1)including a sidewall (36); a moulded plastic lid (2); the lid (2) andthe base (1) defining between them a circumferential inter-engagementzone; the lid (2) having at the inter-engagement zone at least oneengagement member (24) with an engagement face (38) directed generallyaway form the base (1); the base (1) having at the inter-engagement zoneat least one engagement member (39) with an engagement face (40)directed generally away from the lid (2); an electrical heating element(4) mounted in the base (1); and an elastomeric sealing ring (29)arranged on assembly, around the circumferential inter-engagement zone,between the base (1) and the lid (2); wherein the lid-engagement andbase-engagement members (24, 39) engage via their engagement faces (38,40) with resilient deformation of at least one of the lid-engagement andbase-engagement members (24, 39) on assembly of the lid (2) to the base(1) so as to compress the sealing ring (29) for sealing contact withboth the base (1) and the lid (2); and wherein the lid includes at leastone upstanding flange (31, 32) for reinforcement of the lid to exertcompression on the sealing ring.
 21. A steam generator according toclaim 20, wherein the anti-disengagement surface (42) is provided on arib (41) on the lid-engagement member (24).
 22. A steam generatorcomprising:a moulded plastic material base (1) including a sidewall(36); a moulded plastic material lid (2);the lid (2) and the base (1)defining between them a circumferential inter-engagement zone; the lid(2) having at the inter-engagement zone at least one engagement member(24) with an engagement face (38) directed generally away from the base(2); the base (2) having at the inter-engagement zone at least oneengagement member (39) with an engagement face (40) directed generallyaway from the lid (1); an electrical heating element (4) mounted in thebase (2); an elastomeric sealing ring (29) arranged on assembly, aroundthe circumferential inter-engagement zone, between the base (2) and thelid (1);the lid- and base-engagement members (24, 39) engaging via theirengagement faces (38, 40) with resilient deformation of either or bothof the lid- and base-engagement members (24, 39) on assembly of the lid(1) to the base (2) so as to compress the sealing ring (29) for sealingcontact with both the base (2) and the lid (1); the engagement face (38,40) of at least one of the lid- and base-engagement members (24, 39)being a lip (38) adapted and arranged to engage the correspondingengagement face (40) of the other engagement member(s); one of the lid-and base-engagement members (24, 39) extending generally towards thebase (2) or the lid (1) respectively and the other of the lid- andbase-engagement members (24,39) extending adjacent to the one of theengagement members (24, 39); the lid- and the base-engagement members(24, 39) being circumferentially discontinuous around the lid (1) andthe base (2) and provided, circumferentiall around the lid (1) and thebase (2), as a plurality of individual engagement members (24, 39); andapertures for the one of the lid- and base-engagement members (24, 39)being provided at the other of the lid- and base engagement members (24,39).
 23. A steam generator for generating steam at a pressure greaterthan ambient atmospheric pressure, comprising:a moulded plastic base (1)including a sidewall (36); a moulded plastic lid (2);the lid (2) and thebase (1) defining between them a circumferential inter-engagement zone;the lid (2) having at the inter-engagement zone at least one engagementmember (24) with an engagement face (38) directed generally away formthe base (1), when assembled thereto; the base (1) having at theinter-engagement zone at least one engagement member (39) with anengagement face (40) directed generally away from the lid (2), whenassembled thereto; an electrical heating element (4) mounted in the base(1); an elastomeric sealing ring (29) arranged on assembly, around thecircumferential inter-engagement zone, between the base (1) and the lid(2);the lid-engagement and base-engagement members (24, 39) engaging viatheir engagement faces (38, 40) with resilient deformation of either orboth of the lid-engagement and base-engagement members (24, 39) onassembly of the lid (2) to the base (1) so as to compress the sealingring (29) for sealing contact with both the base (1) and the lid (2),for containing steam in the generator at a pressure greater than anambient atmospheric pressure; a steam conduit (P); and connection means(21) for connection to the steam conduit (P) for providing the steamfrom the generator at the pressure greater than the ambient atmosphericpressure.